1. Field of the Invention
The present invention relates to a method and apparatus for controlling a clutch for vehicles.
2. Description of the Prior Art
There is known a vehicular automatic transmission system in which gear-shifting operations of a gear transmission are automatically controlled by means of an electronic control system and the operation of the clutch is also controlled automatically in relation to the gear-shifting operations. In most conventional automatic systems, when fuel-powered operation of the engine stops because, for example, the ignition key has been turned off, control of the transmission and the like is discontinued while supply of electric power to the associated electronic control unit is maintained.
With this conventional arrangement, when fuel-powered operation of the engine stops because, for example, the ignition switch has been turned off, rotation of the engine will halt if the transmission is in the neutral position or the clutch is disengaged, even if the vehicle is running. This results in malfunctioning of the power steering system and the power braking system. To overcome these disadvantages, there has been proposed a control system in which the clutch is engaged after the transmission is shifted into a prescribed gear position other than the neutral position when fuel-powered operation of the vehicle engine stops in the case where the vehicle is running (see, for example, U.S. Pat. No. 5,005,687 and European Patent Application Public Disclosure No. 314409).
However, the proposed system operates so as to maintain the supply of the electric power to the control systems for the transmission and the clutch so as to carry out the aforesaid clutch and transmission control operations even after the ignition switch is turned off and fuel-powered operation of the engine stops. It follows, therefore, that engine braking power is applied to the vehicle when the clutch is engaged. This will cause sudden braking of the vehicle, which may be dangerous to the occupant(s).